A 5th-Generation (5G) core network is based on services that are referred to as network functions (NFs). An NF is a software-implemented component that provides a network-related service such as routing, mobility management, session management, authorization, policy control, and so forth.
Session management in a 5G system is performed by a network function called a session management function (SMF). The SMF coordinates with another network function, called a charging function (CHF), to implement billing to subscriber accounts. While managing a data connection, the SMF repeatedly queries the CHF to reserve data units for the data connection and to report the amount of data that has been used by the data connection. The CHF communicates with the carrier's billing system to enter charges based on the reported amounts of consumed data.
At times, however, the CHF may be unavailable, due to issues such as network failure or congestion, equipment malfunctions, software crashes, etc. During times that the CHF is unavailable, the SMF is unable to reserve data units, and as a result may terminate the data connection, creating an undesirable customer experience.